Method of vulcanizing rubber with heat transfer liquid

Abstract

A heat transfer liquid in the form of a molten salt mixture includes a mixture of potassium nitrate and lithium nitrate, and added calcium nitrate and/or anhydrous salts if appropriate. This is done in order to achieve a low melting point, a low toxicity and in particular a low viscosity. The heat transfer liquid may be used in the vulcanization of rubber.

I claim: 
     
       1. Method of vulcanizing strands of rubber profiles, which comprises: preparing a salt melt of potassium nitrate including a content of lithium nitrate and having a viscosity lower than 40 mPa×s,   heating the salt melt to a temperature substantially between 180° and 260°, and   continuously passing the strands of rubber profiles through the salt melt and vulcanizing the strands of rubber profiles.   
     
     
       2. Method according to claim 1, which comprises adjusting the melting point of the salt melt to below 150° during the salt melt preparation step. 
     
     
       3. Method according to claim 1, which comprises adjusting the viscosity of the salt melt to approximately 25 mPa×s during the salt melt preparation step. 
     
     
       4. Method according to claim 1, which comprises adjusting the content of potassium nitrate in the salt melt to substantially between 55 and 80% by weight during the salt melt preparation step. 
     
     
       5. Method according to claim 4, which comprises adjusting the content of potassium nitrate in the salt melt to substantially between 63 and 73% by weight. 
     
     
       6. Method according to claim 1, which comprises adjusting the content of lithium nitrate in the salt melt to substantially between 20 and 45% by weight during the salt melt preparation step. 
     
     
       7. Method according o claim 6, which comprises adjusting the content of lithium nitrate in the salt melt to substantially between 27 and 37% by weight. 
     
     
       8. Method according to claim 1, which comprises mixing the individual contents of the salt by blending in dry form for obtaining a premix and melting the premix for obtaining a homogeneous phase. 
     
     
       9. Method according to claim 1, which comprises adding the individual contents to an already liquid melt for dissolving in the preparation step.